The present invention relates to the fabrication of thin-walled metal cylinders by electroplating on an expanding mandrel die cylinder and then removing the plated material from the die.
It is known for the fabrication of thin-walled closed or perforated metal cylinders to use a roller-shaped die cylinder, or mandrel, having the dimensions of the hollow cylinder to be fabricated. For making a closed-wall hollow cylinder the entire outer mandrel surface is electrically conducting. For making a perforated hollow cylinder, especially cylindrical screens for the manufacture of screen printing forms, the outer mandrel surface has conductive and non-conductive areas corresponding to the perforations. Damage to the hollow cylinder must be avoided as much as possible. Since the screen cylinders, such as those for making screen printing masks, have relatively large dimensions, the removal of the electro-plated hollow cylinder is a relatively difficult operation. It is therefore known to resiliently expand the mandrel during the fabrication of the cylinder on it. While the removal of the plated hollow cylinder can be thereby aided, nevertheless special means must be provided at the non-expanded edges of the mandrel for removal of the cylinder, by which there is usually lost a portion of the length of the cylinder.
It is an object of the invention to provide a device of the type described above which is so designed that the electroplated hollow cylinder can without special means be removed undamaged from the surface of the mandrel after its fabrication and that practically the entire length of the mandrel can be utilized.